Acoustic wave device

Abstract

In an elastic wave device in which electrodes including interdigital transducers 4 and 5 made of a conductive material are formed on a piezoelectric substrate 1, a dielectric thin film 8 including silicon oxide as its main component is deposited on the interdigital transducers 4 and 5 and a reflector 9 and the thickness of this dielectric thin film 8 is appropriately set. By appropriately setting the thickness of the dielectric thin film 8, it becomes possible to obtain an elastic wave device that is not required to be hermetically sealed in a package for the sake of protecting the electrodes from minute metallic dusts and avoiding influences from the outside.

1 . An elastic wave device in which electrodes including interdigital transducers made of a conductive material are formed on a piezoelectric substrate, comprising a dielectric thin film formed on said interdigital transducers, said dielectric thin film having a thickness of from 100 to 1000 Å and including silicon oxide as its main component.  
     
     
         2 . An elastic wave device in which electrodes including interdigital transducers made of a conductive material are formed on a piezoelectric substrate, comprising a dielectric thin film formed on said interdigital transducers, said dielectric thin film having a thickness of from 100 to 500 Å and including silicon oxide as its main component.  
     
     
         3 . An elastic wave device in which electrodes including interdigital transducers made of a conductive material are formed on a piezoelectric substrate, comprising a dielectric thin film formed on said interdigital transducers, said dielectric thin film having a thickness of from 200 to 500 Å and including silicon oxide as its main component.  
     
     
         4 . An elastic wave device according to  claim 1 ,  2 , or  3 , characterized in that said dielectric thin film is formed with a CVD method.  
     
     
         5 . An elastic wave device according to  claim 1 ,  2 , or  3 , characterized in that said dielectric thin film is formed with a sputtering method.  
     
     
         6 . An elastic wave device according to  claim 5 , characterized in that said dielectric thin film is deposited by placing said piezoelectric substrate or a substrate including a piezoelectric thin film so as to be inclined with respect to a sputtering target and by sputtering said dielectric thin film from a direction that is inclined with respect to a direction vertical to the surface of said substrate.  
     
     
         7 . An elastic wave device according to any one of  claims 1  to  6 , characterized in that electrode fingers that are made of a conductive material and constitute said electrodes including the interdigital transducers have a cross-sectional shape that is a trapezoid when taken along a plane that is parallel to the direction vertical to the surface of said substrate, and in a direction vertical to a crossing width direction thereof.